1. Field of the Invention
The present invention relates to a lens barrel, and more particularly to a lens barrel having a barrier cylinder.
2. Description of the Related Art
In the related art, a retraction type lens barrel which is movable between a retracted state and an extended state is known. In the lens barrel, retraction and extension of a first lens unit located at the side closest to an object are performed by a rotating cam ring. In addition, the lens barrel includes a lens barrier which is located in front of the first lens unit to cover a lens in the retracted state and to expose the lens in an image shooting state (the extended state).
Japanese Patent Laid-open No. 2004-258646 discloses a barrel structure of a zoom lens including a cam ring, a first lens unit frame which is arranged in an outer circumference of the cam ring to be translatorily guided in an optical axis direction, and a light shielding decorative cylinder which is arranged in the outer circumference of the first lens unit frame and includes a lens barrier. The barrel structure of the zoom lens includes a cam groove for a lens unit frame which is formed on an outer circumference surface of the cam ring to be engaged with a cam follower provided in the first lens unit frame and a cam groove for a decorative cylinder which is engaged with a cam follower provided in the light shielding decorative cylinder. The cam follower of the light shielding decorative cylinder passes through a translatory guide groove, which is formed in the first lens unit frame to be parallel to the optical axis, and is engaged with the cam groove for a decorative cylinder. In addition, the cam groove for a lens unit frame and the cam groove for a decorative cylinder have a shape so that the first lens unit frame and the light shielding decorative cylinder are moved along the same trajectory in the optical axis direction in an imaging zone of the zoom lens. Therefore, since the first lens frame and the light shielding decorative cylinder can be allowed to have different cam trajectories from the retracted state to the extended state, the first lens unit can be extended to the space where the lens barrier is arranged after the lens barrier is opened.
However, in the barrel structure disclosed in Japanese Patent Laid-open No. 2004-258646, a cam follower of the first lens unit frame is formed at a position closer to an image plane side than to the translatory guide groove of the first lens unit frame. In addition, a cam groove of the first lens unit frame formed in the outer circumference of the cam ring and a cam groove of the light shielding decorative cylinder are provided to be aligned in the optical axis direction. Therefore, the lengths of the first lens barrel and the cam ring in the optical axis direction are increased, so that the retraction length of the camera is increased.
In addition, in order to reduce the outer diameter of the lens barrel, it is effective to reduce the thickness of the light shielding decorative cylinder. However, if the thickness of the light shielding decorative cylinder is reduced, deformation may easily occur. Therefore, when an external force is exerted on the lens barrel, the cam follower of the light shielding decorative cylinder on which the external force is exerted may be easily disengaged from the cam groove.